instruct是及物动词，在本句中的意思是to give (someone) an order or command，通常用于instruct sb to do sth这个句型中。Her manager instructed her to do her work. 或者She was instructed to do her work. 这是老板给她的指示/命令。然后她按指示做了，She did her work as her manager instructed (her). 或者She did her work as she was instructed (by her manager). 你会发现，无论as分句用主动语态还是被动语态，作宾补或主补的不定式是不能出现的。这个不定式就是as分句的空位。作为一般英语学习者，知道比较分句经常采用缩减形式，熟悉常见的缩减后的比较分句形式就够了，没有必要对每个比较分句都要去分析省略了什么，空位是什么。